Deployable shock-absorbing vehicle struts, or shock struts, for example oleo struts, are used for vehicles such as aircraft and hyperloop pod vehicles. An oleo strut (oleo-pneumatic shock absorbing strut) converts kinetic energy into heat by the use of a gas, providing elastic spring characteristics, and oil for dampening. In aircraft, the oleo strut cushions landing impacts or bump perturbations and dampens repeat oscillations as well as the tendency for an aircraft to rebound or “bounce.” The oleo strut may be mixed or separated, and single-stage or multiple-stage, for example. Other types of shock struts exist, but are not commonly used in the current state of the art. See Currey, Norman S., Aircraft Landing Gear Design: Principles and Practices (1988). For example, an oleo strut for landing gear is disclosed in U.S. Pat. No. 2,279,447 to Cowey, which is hereby incorporated by reference in its entirety.
Aircraft, helicopters, hyperloop vehicles and the like, typically have very limited space for stowing deployable wheel systems and/or landing gear, and positioning deployable wheel systems to engage available space in the aircraft or other vehicle can be challenging.
Prior art systems that address this problem are directed to mechanisms that allow the landing gear shock strut to be compressed, or shortened, prior to stowing the landing gear. The shock strut is then extended after the landing gear is moved out of the stowage volume of the aircraft and prior to landing. Landing gear struts that are configured to shorten the shock absorber for stowage are sometimes referred to as shrink shock struts. For example, in U.S. Pat. No. 5,908,174 to Churchill et al., which is hereby incorporated by reference, an automatic shrink shock strut for an aircraft landing gear is disclosed that is configured to selectively retract the strut shock piston into the cylinder by transferring pressurized hydraulic fluid into a shrink chamber, and to re-expand the shock absorber prior to landing by transferring pressurized gas into a gas spring chamber to force hydraulic fluid out of the shrink chamber.
In U.S. Pat. No. 7,942,366 to Waide, a shock strut is disclosed having a shock absorber with a dedicated center channel defined in the cylinder of the shock absorber, and a coaxial motor configured to drive a nut rotatably attached at the top end of the cylinder. A lead screw engages the nut, such that the length of the strut can be modified by adjusting the portion of the lead screw that is in the center channel. In another embodiment, the motor is mounted at the top of the lead screw and configured to drive the lead screw. However, in either case, the middle portion of the shock absorber is not available to provide the desired shock absorbing and energy dissipation, and would therefore diminish the functionality of the shock strut.